You youngins probably don’t remember this, but a few years ago there was an arms race on Kickstarter to create the smallest Arduino-compatible microcontroller board. Since then, a few people have realized they can make more money on Kickstarter through fraud or potato salad, and the race to create the smallest ‘duino board petered out.
It’s a shame [Meizhu] wasn’t part of the great miniature Arduinofication of Kickstarter, because this project would have won. It’s an Atmel ATtiny85, with USB port, resistors, diodes, reset button, LED, and pin headers, that is just 72 mils larger than the PDIP package of the ‘tiny85. Outside of getting a bare die of ‘tiny85s, there isn’t much of a chance of this board becoming any smaller.
[Meizhu] was inspired to create this board from [Tim]‘s Nanite 85, which up until a few days ago was the current champion of micro microcontroller boards. With a bit of work in KiCAD, the new board layout was created that is just a hair larger than the 0.4″ x 0.4″ footprint of the PDIP ATtiny85. There were a few challenges in getting a working board this small; you’d be surprised how large the plastic bits around pin headers are, but with some very crafty soldering, [Meizhu] was able to get it to work.